A unique transcription factor for the A alpha fibrinogen gene is related to the mitochondrial single-stranded DNA binding protein P16

Supplementing L-Citrulline Can Extend Lifespan in C. elegans and Attenuate the Development of Aging-Related Impairments of Glucose Tolerance and Intestinal Barrier in Mice

L-Citrulline (L-Cit) is discussed to possess a protective effect on intestinal barrier dysfunction but also to diminish aging-associated degenerative processes. Here, the effects of L-Cit on lifespan were assessed in C. elegans, while the effects of L-Cit on aging-associated decline were determined in C57BL/6J mice. For lifespan analysis, C. elegans were treated with ±5 mM L-Cit. Twelve-month-old male C57BL/6J mice (n = 8-10/group) fed a standard chow diet received drinking water ± 2.5 g/kg/d L-Cit or 5 g/kg/d hydrolyzed soy protein (Iso-N-control) for 16 or 32 weeks. Additionally, 4-month-old C57BL/6J mice were treated accordingly for 8 weeks. Markers of senescence, glucose tolerance, intestinal barrier function, and intestinal microbiota composition were analyzed in mice. L-Cit treatment significantly extended the lifespan of C. elegans. The significant increase in markers of senescence and signs of impaired glucose tolerance found in 16- and 20-month-old control mice was attenuated in L-Cit-fed mice, which was associated with protection from intestinal barrier dysfunction and a decrease in NO2- levels in the small intestine, while no marked differences in intestinal microbiota composition were found when comparing age-matched groups. Our results suggest that pharmacological doses of L-Cit may have beneficial effects on lifespan in C. elegans and aging-associated decline in mice.

Fibrinogen gene regulation

The Aα, Bβ and γ polypeptide chains of fibrinogen are encoded by a three gene cluster on human chromosome four. The fibrinogen genes (FGB-FGA-FGG) are expressed almost exclusively in hepatocytes where their output is coordinated to ensure a sufficient mRNA pool for each chain and maintain an abundant plasma fibrinogen protein level. Fibrinogen gene expression is controlled by the activity of proximal promoters which contain binding sites for hepatocyte transcription factors, including proteins which influence fibrinogen transcription in response to acute-phase inflammatory stimuli. The fibrinogen gene cluster also contains cis regulatory elements; enhancer sequences with liver activities identified by sequence conservation and functional genomics. While the transcriptional control of this gene cluster is fascinating biology, the medical impetus to understand fibrinogen gene regulation stems from the association of cardiovascular disease risk with high level circulating fibrinogen. In the general population this level varies from about 1.5 to 3.5 g/l. This variation between individuals is influenced by genotype, suggesting there are genetic variants contributing to fibrinogen levels which reside in fibrinogen regulatory loci. A complete picture of how fibrinogen genes are regulated will therefore point towards novel sources of regulatory variants. In this review we discuss regulation of the fibrinogen genes from proximal promoters and enhancers, the influence of acute-phase stimulation, post-transcriptional regulation by miRNAs and functional regulatory variants identified in genetic studies. Finally, we discuss the fibrinogen locus in light of recent advances in understanding chromosomal architecture and suggest future directions for researching the mechanisms that control fibrinogen expression.

Identification and characterization of endonuclein binding proteins: evidence of modulatory effects on signal transduction and chaperone activity

Background

We have previously identified endonuclein as a cell cycle regulated WD-repeat protein that is up-regulated in adenocarcinoma of the pancreas. Now, we aim to investigate its biomedical functions.

Results

Using the cDNA encoding human endonuclein, we have expressed and purified the recombinant protein from Escherichia coli using metal affinity chromatography. The recombinant protein was immobilized to a column and by affinity chromatography several interacting proteins were purified from several litres of placenta tissue extract. After chromatography the eluted proteins were further separated by two-dimensional gel electrophoresis and identified by tandem mass spectrometry. The interacting proteins were identified as; Tax interaction protein 1 (TIP-1), Aα fibrinogen transcription factor (P16/SSBP1), immunoglobulin heavy chain binding protein (BiP), human ER-associated DNAJ (HEDJ/DNAJB11), endonuclein interaction protein 8 (EIP-8), and pregnancy specific β-1 glycoproteins (PSGs). Surface plasmon resonance analysis and confocal fluorescence microscopy were used to further characterize the interactions.

Conclusions

Our results demonstrate that endonuclein interacts with several proteins indicating a broad function including signal transduction and chaperone activity.

An ordered array of cold shock domain repressor elements across tumor necrosis factor-responsive elements of the granulocyte-macrophage colony-stimulating factor promoter

The tumor necrosis factor-alpha-responsive region of the human granulocyte-macrophage colony-stimulating factor (GM-CSF) promoter (-114 to -31) encompasses binding sites for NF-kappaB, CBF, AP-1, ETS, and NFAT families of transcription factors. We show both here and previously that mutation of any one of these binding sites greatly reduces tumor necrosis factor-alpha induction of the GM-CSF promoter. Interspersed between these elements are sequences that when mutated lead to an increase in GM-CSF promoter activity. We have previously shown that two of these repressor elements bind proteins known as cold shock domain (CSD) factors and that overexpression of CSD proteins leads to repression of GM-CSF promoter activity in fibroblasts. CSD proteins are single strand DNA- and RNA-binding proteins that contact 5'-CCTG-3' sequences in the GM-CSF repressor elements. We show here that two newly identified repressor sequences in the proximal promoter can also bind CSD proteins. We have characterized the CSD-containing protein complexes that bind to the GM-CSF promoter and identified a novel protein related to mitochondrial single strand binding protein that forms part of one of these complexes. The four CSD-binding sites on the promoter occur in pairs on opposite strands of the DNA and appear to form an ordered array of binding elements. A similar ordered array of CSD sites are present in the promoters of the granulocyte colony-stimulating factor and interleukin-3 genes, implying a common mechanism for negative regulation of these myeloid growth factors.

Cell type-specific regulation of fibrinogen expression in lung epithelial cells by dexamethasone and interleukin-1beta

Our recent studies demonstrating the expression of fibrinogen (FBG) by an alveolar type II cell line stimulated with proinflammatory mediators and also in the inflamed pulmonary epithelium of animals with Pneumocystis carinii pneumonia suggest that extrahepatic FBG participates in the local acute phase response (APR) to infection and subsequent wound repair. However, the mechanisms that regulate extrahepatic FBG expression are poorly understood. This study compares the regulation of hepatic and pulmonary FBG expression by mediators of the APR, interleukin (IL)-6, IL-1beta, and dexamethasone (DEX), a synthetic glucocorticoid. Northern blotting and metabolic labeling studies revealed that IL-6 with or without DEX upregulates gammaFBG messenger RNA and protein, whereas IL-1beta inhibits gammaFBG expression in human lung (A549) and liver (HepG2) epithelial cells. In contrast, the addition of DEX relieved the IL-1beta-mediated inhibition of FBG expression in lung epithelial cells only; this response is termed "DEX rescue." Studies with cycloheximide indicate that only DEX rescue required de novo protein synthesis. Nuclear run-on analysis revealed no increase in gammaFBG transcription by DEX treatment. Although DEX treatment alone increased the stability of gammaFBG transcripts in lung cells, this effect was not observed in the presence of IL-1beta. Together, these results suggest that pre-existing transcription factors mediate the effects of IL-6 with or without DEX, DEX, and IL-1beta on gammaFBG gene expression in lung and liver cells. Also, the data suggest that DEX induces new protein synthesis of an inhibitor of IL-1beta signal transduction to effectively "rescue" FBG production in lung but not liver epithelial cells. This cell type-specific stimulation of FBG production by glucocorticoids to overcome IL-1beta inhibition may promote pulmonary wound repair mechanisms.

A sequence-selective single-strand DNA-binding protein regulates basal transcription of the murine tissue inhibitor of metalloproteinases-1 (Timp-1) gene

Tissue inhibitor of metalloproteinases-1 (TIMP-1) is important in maintaining the extracellular proteolytic balance during tissue remodeling processes. To allow homeostatic tissue turnover, the murine Timp-1 gene is expressed by most cells at a low basal level, and during acute remodeling its transcription is activated by a variety of stimuli. A non-consensus AP-1-binding site (5'-TGAGTAA-3') that is conserved in mammalian timp-1 genes is a critical element in basal and serum-stimulated transcription. We show here that each strand of this unusual AP-1 site binds a distinct single-stranded DNA-binding protein, although neither strand from a perfect consensus AP-1 site from the human collagenase gene shows similar binding. One of the single-strand binding factors, which we term ssT1, binds to a second upstream Timp-1 region between nucleotides -115 and -100. Deletion analysis demonstrated that this region is important in basal but not serum-inducible transcription. The ssT1 factor was 52-54 kDa by UV cross-linking of electrophoretic mobility shift assays and Southwestern blot analysis. Its binding to DNA shows sequence selectivity rather than specificity, with 5'-CT/ATTN((4-6))ATC-3' as a favored motif. Multiple ssT1-like activities were found in nuclear extracts from mouse fibroblasts and rat liver and testis, suggesting that these factors may regulate basal Timp-1 transcription in a tissue-specific fashion.

The gene and processed pseudogenes of the rat mitochondrial single-strand DNA-binding protein: structure and promoter strength analyses

The gene for the rat mitochondrial single-stranded DNA-binding protein (mtSSB) was amplified by PCR and isolated as several overlapping genomic clones. The clones encompassed the 5' untranslated sequence and all intron/exon junctions. The gene contained seven exons and six introns. The first exon contained only 5' untranslated sequence. The 16-amino acid mitochondrial targeting presequence, encoded by the second and third exons, was precisely bisected by intron 2. All intron donor and acceptor sites were consistent with the GT/AG consensus. The transcription start site was determined by primer-extension analysis to be 69bp upstream of the translation start codon. The upstream sequence lacked TATA and CCAAT boxes at the expected locations, but did contain several other potential regulatory elements including a GC box (Sp1-binding site) and three NRF-2 sites, one of which was located precisely beside the transcription start site. A 10 out of 12 imperfect NRF-1 site was located within the first exon. The 5' flanking sequence (-546 to +30) was shown to have strong promoter activity in transient transfection assays in primary rat hepatocytes and HepG2 cells. In addition, evidence for the existence of several mtSSB processed pseudogenes was obtained. These pseudogenes lacked introns and contained substitution and deletion mutations compared to the cDNA sequence. The 5' upstream region of one of the pseudogenes was analyzed and found to contain negligible promoter activity.